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How to Clean a Bike Chain

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How to Adjust a Bike Saddle (Seat)

How to Adjust a Rear Derailleur

You may need to adjust your rear derailleur if you have problems shifting between gears on the rear gear hub, such as:

Skipped gears: Gears jump unexpectedly from one gear to another, out of sequence.
Gears that won’t engage: It’s impossible to shift into certain gears, as if the gears are blocked.
Delayed shifting: Gears engage, but only after an extended delay (at least a few seconds).

How to Inspect Your Gears

If you suspect you may need to adjust your rear derailleur, first inspect your gears in action.

Take a slow ride on your bike. As you ride, shift through every gear on the rear gear set (usually 5–10 gears) and through each chain ring. For instance, if you have three chain rings and your rear gear set has seven gears, shift through all 21 possible gears.
Whenever you encounter a shifting problem, stop pedaling and make a note of the gears on which the problem occurred. Note the problem gear(s) on both the chain ring and the rear gear set.

The front derailleur may need adjustment, or the chain ring may need to be cleaned or replaced. Both of these jobs are best done by a mechanic.

The rear derailleur probably needs adjusting, which you can do with the help of a friend.

Inspect the derailleur: Check to see whether it’s been bent in toward the bike frame. If the derailleur is damaged or bent, a serious repair is required, and you should bring the bike to a mechanic.
Find the barrel adjuster: This small dial allows you to fine-tune the derailleur’s responsiveness. Tightening the dial improves shifting from smaller gears to larger gears. Loosening it improves shifting from larger gears to smaller gears. Your goal in steps 3–6 is to find the barrel adjuster setting that lets all the gears on the rear hub shift smoothly.
Prop up the rear wheel: Have a friend lift the bike up from the saddle. Then stand next to the bike and pedal with one foot while also shifting through the gears with a free hand.
If you encounter a shifting problem: Stop pedaling and have your friend let down the bike.
Turn the barrel adjuster: Turn the adjuster a half-turn counterclockwise (when facing the dial from behind the bike) to tighten, or a half-turn clockwise to loosen.
Pedal and shift through the gears again: Stop pedaling and shifting and repeat step 5 until you find the correct setting. You’ll know you’ve found it when the problematic gears shift smoothly. The other gears shouldn’t be thrown off by your adjustment. If adjusting the derailleur doesn’t solve the problem, seek the help of a bike mechanic.